The Transport Select Committee published a critical report in the summer, claiming that the government should not proceed with ‘all lane running’ schemes while major safety concerns exist.

The group of cross party watchdog MPs has launched a new attack on the Department for Transport after they approved an all lane running scheme on a 32-mile stretch of the M4 before its response to their report could be considered.

Officials are eager to press ahead with the smart motorway plans, which are already in operation on sections of the M42, M1, M6 and M5. It is their plan to boost capacity without widening roads.

Plans are place to convert the hard shoulder into a running lane on around 300 miles of motorway, with a programme of 30 schemes costing £6bn over the nine years.

However, the Committee has argues that the conversion of the hard shoulder into a permanent running lane is a radical change to the nature of motorways and it would create a real challenge for motorists.

Chair of the Transport Select Committee, Louise Ellman said: “The Department for Transport is blatantly ignoring the safety concerns set out in our report. We had barely had the response to our report before the government endorsed an all lane running scheme on the M4.”

She continued: “The committee isn’t arguing with government about the need for more capacity on our motorways, or their statement that motorways are our safest roads. But we take real issue with the government’s assertion that all lane running schemes on motorways are no different to other types of roads without hard shoulders.

“Motorways are a different class of road and drivers have different expectations when using them. The Committee remains concerned about the size and spacing of Emergency Refuge Areas. While we are pleased that Highways England has committed to a review, the M4 proposal should not have gone ahead until the review is complete.”

Ellman concluded by saying: “We are not the only people who are worried about this incarnation of all lane running schemes. In the course of our inquiry, there was genuine concerns raised by the emergency services, road workers and recovery operators. The government cannot ignore them.”